This invention relates to filtration processes and equipment, and more particularly to filter presses, such as those used in slurry dewatering processes during minerals processing.
Filter presses generally comprise a horizontally-arranged stack of vertically extending filter plates which are separated by a small space when the filter press stack is fully opened for cake discharge. Each filter plate comprises respective filter cloths on its opposing sides. In order to facilitate installation or removal of the filter cloths, it is necessary to lift the very heavy and sizeable filter plate assemblies and in some instances, completely extract them from the horizontally-arranged stack to gain access to the securing mechanisms which join the filter cloth to the filter plate. An example of such a filter plate assembly is shown in U.S. Pat. No. 5,851,387, which is incorporated herein by reference.
FIGS. 1 and 2 illustrate respective front plan and isometric cross-sectional views of one example of a conventional filter plate assembly 9, and conventional feed eye assembly 940, which require complete extraction from a filter press during filter cloth 968 replacement. Conventional filter plate assembly 9 comprises a first filter plate 100 defined by a base portion 104 having standoffs 120, peripheral walls 130, and a shelf portion 108. The shelf portion 108 is generally composed of a seat surface 101, a recess 102, a tapered surface 103, and a feed eye aperture 110. Chamfers 112 surround the feed eye aperture 110, and a plurality of bores 106 are provided within the shelf portion 108.
The conventional filter plate assembly 9 further comprises a conventional feed eye assembly 940. The conventional feed eye assembly 940 comprises, on one side, a filter cloth 968 having an aperture 968B therein, and a separate retaining ring 990 having a radial projection 998 and a ring protrusion 999 extending therefrom, which is configured to be received within the aperture 968B of filter cloth 968. Retaining ring 990 comprises a ring protrusion end 991, a ring protrusion outer wall 994, a ring protrusion inner wall 995, a shelf 996, an inner surface 993, and one or more head clearance holes 992. A backer plate ring 975 having one or more shaft clearance holes 997 may be positioned within the retaining ring 990.
The conventional feed eye assembly 940 comprises, on an opposite side, a holding ring 970 comprising a radial projection 971 and a barrel 979, extending therefrom, which is configured to be received within the aperture 968B of a filter cloth 968. The holding ring 970 further comprises an inner surface 973, a shelf 981, one or more head clearance holes 976, a chamfer surface 978, a barrel inner wall 980, a barrel outer wall 982, and a barrel end 983. A backer plate ring 975 having one or more shaft clearance holes 977 may be positioned within the holding ring 970.
The ring protrusion 999 of the retaining ring 990 and the barrel 979 of the holding ring 970 pass through the apertures 968B of respective filter cloths 968 such that the inner surfaces 973, 993 of the radial projections 971, 998 abut an annular surface of the filter cloth 968 and such that the barrel outer wall 982 and ring protrusion outer wall 994 are surrounded by filter cloth apertures 968B. When assembled, the barrel end 983 rests against the shelf 996, the barrel outer wall 982 engages ring protrusion inner wall 995, and ring protrusion end 991 rests against shelf 981.
One or more fasteners 974 pass through head clearance holes 976, 992 and shaft clearance holes 977, 997 of the holding ring 970 and retaining ring 990, respectively, and engage the bores 106 in the first filter plate 100. When fasteners 974 are tightened, the filter cloths 968 are secured to the filter plate 100 by virtue of the retaining properties of radial projections 971, 998. Because a large amount of space is needed to gain access to and remove fasteners 974, it is very difficult or nearly impossible to change filter cloths 968 on such assemblies 9, even when the filter plates 100 are separated by their maximum distance. Moreover, the use of two different geometries for retaining ring 990 and holding ring 970 increases manufacturing and inventory costs.